vp9: Refactor some denoiser logic in vp9_pick_inter_mode.

Move the logic for rechecking zeromv on denoised block out to simplify
the function. To simplify the param passing, add a new structure
VP9_PICKMODE_CTX_DEN which is only used when denoiser is enabled.

Change-Id: Iaa9b4396dfcb8147236c02d4a1868a09103a4476
2 files changed